Diameter expansion method of straight seam welded pipe

The diameter expansion of lsaw pipe is a pressure processing technology that uses hydraulic or mechanical means to apply force from the inner wall of the steel pipe to expand the steel pipe outward in the radial direction. The mechanical method is simpler and more efficient than the hydraulic method. The diameter expansion process of several of the most advanced large-diameter straight seam welded pipe pipelines in the world is adopted. The process is:

Mechanical diameter expansion uses the segmented sector block at the end of the diameter expander to expand in the radial direction, so that the pipe blank can achieve plastic deformation of the entire pipe length in a step-by-step manner along the length direction. Divided into 5 stages
1. Preliminary rounding stage. The sector blocks are opened until all the sector blocks are in contact with the inner wall of the steel pipe. At this time, the radius of each point in the inner circular tube of the steel pipe within the step range is almost the same, and the steel pipe is initially rounded.
2. Nominal inner diameter stage. The sector block starts to reduce its movement speed from the front position until it reaches the required position, which is the inner circumferential position of the finished pipe with quality requirements.
3. Rebound compensation stage. The sector block starts from the second stage position and further reduces the speed until it reaches the required position. This position is the inner circumferential position of the steel pipe before rebound required by the process design.

4. Pressure stabilization stage. The sector-shaped block remains stationary in the inner circumferential position of the steel pipe for a period of time before springing back. This is the pressure-maintaining and stable stage required by the equipment and diameter expansion process.
5. Unloading return stage. The sector block rapidly retracts from the inner circumferential position of the steel pipe before rebounding until it reaches the initial diameter expansion position, which is the minimum contraction diameter of the sector block required by the diameter expansion process.